1. Field of the Invention
The present invention relates to a method of manufacturing a pipe liner bag for use in repair of an old pipe.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. The pipe lining method utilizes a tubular pipe liner bag made of a resin absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipe to be repaired by means of a pressurized fluid such that the pipe liner bag is turned inside out as it proceeds deeper in the pipe. Hereinafter, this manner of insertion shall be called "everting." When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the everted tubular liner is pressed against the inner wall of the pipe by a pressurized fluid, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
The pipe lining material for use in the foregoing pipe lining method may be manufactured by a method proposed, for example, in Japanese Patent Publication No. 58-33098 (corresponding PCT Patent Publication No. WO80-00720). Specifically, this method involves joining, by sewing, both sides of a strip laminate having a resin absorbent material and an opaque layer made of a plastic film or the like overlaid on one surface of the resin absorbent material, and adhering a sealing ribbon tape or the like to the joined portion of the strip to form a tubular pipe liner bag.
This manufacturing method employs lock sewing for the sewing of the resin absorbent material, so that a sewing yarn appears in a portion of the resin absorbent material sewed by the lock sewing on both sides of the seam over a constant width. Then, the sealing ribbon tape is adhered or welded on the opaque layer near the joined surface to seal the seam. In this event, the sealing ribbon tape is pressed onto the opaque layer from above the sewing yarn to adhere or weld the sealing ribbon tape to the opaque layer.
However, since the sewing yarn appears on the surface of the opaque layer, the sealing ribbon tape covered over the appearing sewing yarn and pressed onto the opaque layer for adhesion or welding will result in the sewing yarn cutting into the sealing ribbon tape, causing pin holes formed through the sealing ribbon tape.
Also, even if the sealing ribbon tape is adhered to the opaque layer with an adhesive, the difference in material between the sewing yarn and the opaque layer prevents the sealing ribbon tape, although adhering to the opaque layer, from adhering to the sewing yarn. For this reason, a sealing ribbon tape having a width larger than the sewing width of the resin absorbent material must be used to adhere to the opaque layer beyond the seam.
The above-mentioned sealing method, however, is highly susceptible to formation of pinholes, and also involves complicated works.